This is an array of (EVENT:USED) flags associated with the corresponding labels, indicating whether the event is general purpose (value non-zero) or has specific purpose (value zero).  General-purpose events may have free-entry text labels and descriptions, whereas those of specialized events tend to be fixed.  The values used are defined by the application that creates and processes the data, their values are not described as part of the C3D file format because events are normally application and trial environment specific.